Starting on 21 April 2012, WHO is uniting countries across the globe for a week of vaccination campaigns, public education and information sharing under the umbrella of World Immunization Week.

Immunization is one of the most successful and cost-effective health interventions and prevents debilitating illness, disability and death from vaccine-preventable diseases such as diphtheria, hepatitis A and B, measles, mumps, pneumococcal disease, polio, rotavirus diarrhoea, tetanus and yellow fever.